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Performance and Applications of an Ensemble of Atomic Fountains

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Conference paper

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The United States Naval Observatory USNO has four rubidium fountains that have been in operation for the past 1.7 years. Fountain performance and applications to timekeeping and to tests of Local Position Invariance are presented. Atomic timescales benefit from averaging a large number of clocks. Globally, more than 300 atomic clocks contribute to the generation of International Atomic Time TAI, and locally dozens of institutions maintain their own ensemble of clocks for precise time. These clocks are predominantly commercial cesium beam clocks and commercial hydrogen masers. The first cold-atom clocks to find application to timekeeping are atomic fountains, which have been contributing to TAI as primary frequency standards and in some cases have been incorporated into local timescales. Because they serve as primary standards, periods of evaluation of frequency biases are necessary still, some systems seem to achieve more-or-less continuous operation. At some institutions, only one fountain clock contributes to the ensemble at a given time, although two clocks at PTB and three at SYRTE seem to run regularly. At the U. S. Naval Observatory USNO, four rubidium atomic fountains have been built to use in the timing ensemble and two more fountains are close to being operational. These devices run continuously, without systematic evaluations, and serve as stable frequency references for timing applications as opposed to absolute frequency standards. The continual operation of the ensemble of fountains should result in improved performance, as well as reliability and robustness, compared to a single device.

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  • Test Facilities, Equipment and Methods
  • Atomic and Molecular Physics and Spectroscopy

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